I use Jersey with flash uploader and the problem I met is that I need to determine “file partialy uploaded” situation ’cause user has an opportunity to cancel it at any time. All solutions that I found for this problem were on PHP (look for The uploaded file was only partially uploaded text). I didn’t find any standart technics how to get size of uploaded file (uploaded file’s input stream doesn’t has such information) to compare it with actual file size. So I used a “little reflection magic” to get it. ’cause classes that we’ll use to get information is private for org.jvnet.mimepull package we need to create out util class in exactly the same package. Then we can use reflection to get any infomation that we need.